The high-pressure pump is generally provided with a plunger which reciprocates along with a camshaft of an engine. Specifically, when the plunger slides down from its top dead center to its bottom dead center, a fuel in a fuel gallery is suctioned into a compression chamber (suction stroke). When the plunger slides up from the bottom dead center to the top dead center, a part of the low-pressure fuel is returned to the fuel gallery (metering stroke). Then, after a suction valve is closed, when the plunger further slides up, the fuel in the compression chamber is compressed (compression stroke).
As an engine speed becomes high and a rotational speed of a camshaft also becomes high, the plunger reciprocates at high speed. As a result, a variation in fuel pressure in a fuel gallery is made large to generate a pulsation.
Japanese Patent No. 4036153 (U.S. Pat. No. 7,124,738B2) shows a high-pressure pump having a pulsation damper in a fuel gallery to attenuate a pulsation of fuel. The pulsation damper is a diaphragm made of metallic material.
The diaphragm moves inward or outward in accordance with a differential pressure between a gas pressure applied to an inner surface of the diaphragm and the fuel pressure applied to an outer surface of the diaphragm. Thereby, the pulsation damper is deformed inward or outward to restrict the fuel pulsation. For example, in the metering stroke, when the fuel in the compression chamber is returned to the fuel gallery so that the fuel pressure in the fuel gallery increases, the pulsation damper is deformed inward to restrict an increase in fuel pressure.
In the high-pressure pump shown in Japanese Patent No. 4036153 (U.S. Pat. No. 7,124,738B2), since a fuel passage communicating to an upper space of the damper is restricted by a damper supporting member and a lid member, a large part of the fuel returning to a fuel gallery in a metering stroke flows in a lower space of the damper. Further, since a fuel inlet is formed at a lower space of the damper, when the fuel flow velocity is increased, it is likely that the fuel flows to the fuel inlet before the damper is deformed to restrict a fuel pressure increase. In such a case, the fuel pressure pulsation is transmitted to a fuel pipe and a fuel pipe supporting member, which may cause noise problems. If a resonance arises in the fuel pipe supporting member, the fuel pipe supporting member may be damaged.